Scalesia

© Herbarium, University of Cambridge, UK

On the Galápagos, Darwin found plants that were related to daisies and sunflowers--but grew to the size of trees. Like the marine iguanas, these island residents seemed to have adapted to their environment: with plenty of sun and little competition, daisies and cactuses could grow to the size of trees.

Darwin noticed another "truly wonderful fact" about these giant daisy relatives. He had found six species, now classified in the genus Scalesia, and remarkably, "not one of these six species grows on any two islands." It was not enough that they were found only on the Galápagos--each species was found on only one island. The same was true of dozens of other plants. What could account for this diversity?

Birds of a Feather

Darwin was intrigued that almost all the birds on the Galápagos resembled birds from the mainland. The chief difference was in their coloring. Most tropical birds have bright plumage, but on the grim Galápagos islands, the birds were "generally more dusky colored." Like the iguanas, they seemed to have adapted to match the dark lava around them.

A rare exception was the brightly colored vermilion flycatcher. Perhaps it was not a true Galápagos bird, Darwin thought: "It is worthy of remark, that the only land-bird with bright colours, is that species of tyrant-flycatcher, which seems to be a wanderer from the continent." It appeared that only species found solely on the Galápagos were colored to match its lava backdrop.